554 



stretches from 12° to 18° ; and in the Cordil- 

 leras of Guatimala and Mexico from 9° to 

 191° of latitude. I saw at the north-west ex- 

 tremity of the basin of the West Indies 

 the secondary formations dip towards the 

 south-east; along the coast of Venezuela, 

 rocks of gneiss and primitive mica-slate 

 dip towards the north-west. The basalts, 

 amygdaloides, and trachytes, which are 

 often surmounted by tertiary lime-stones, 

 appear only towards the eastern and western 

 banks. 



i. The Basin of the Lower Oroonoko, or 

 the Plains of Venezuela. This basin, like 

 the plains of Lombardy, is open to the 

 east. Its limits are the chain of the shore of 

 Venezuela on the north ; the eastern Cordil- 

 lera of New Grenada on the west ; and the 

 Sierra Pari me on the south ; but as the latter 

 groupe extends on the west, only to the me- 

 ridian of the cataracts of Maypures (long. 

 70° 370 ^ there remains an opening or land- 

 strait, running from north to south, by 

 which the Llanos of Venezuela communicate 

 with the basin of the Amazon and the Rio 

 Negro. We distinguish between the basin of 

 the Lower Oroonoko properly so called (on the 

 north of that river and the Rio Apure), and 

 the plains of Meta and Guaviare. The latter 



